#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char rbuf[512*1024];

char*mmap();
#define RD(v) int v=0;{int c;while(c=*r++-48,c>=0)v=v*10+c;}
#define RDL(v) long v=0;{int c;while(c=*r++-48,c>=0)v=v*10+c;}

main(){
	int rsize=read(0,rbuf,sizeof rbuf);
	char*r=rbuf;
	RD(n);
	RD(m);
	r=rbuf+(rsize-1);
	int z=1;
	while(m--){
		--r;
		int i=*r---0x30;
		if(*r>=0x30){
			i+=(*r---0x30)*10;
		}
		if(z==1) z=i;
		else if(i>=z) --z;
	}
	printf("%d",z);
}